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S4TC OF CfALIFORNIA-ENVIRONMENTAL PROTE44wrENCY PETE IMLSON,Ci� <br /> DEPARTMENT OF TOXIC SUBSTANCES CONTROL <br /> 10161 CROYDON WAY,SUITE 3 <br /> SACRAMENTO,CA 96827-2106 <br /> (510)' 540-3827 <br /> June 20 , 1996 <br /> Mr. Robert Chambers <br /> Beck Development Company <br /> 2114 West Hammer Lane <br /> Stockton, California 95209 <br /> BECK DEVELOPMENT COMPANY, TRACY SITE, HAZARDOUS WASTE PROPERTY <br /> DETERMINATION co""l <br /> Dear Mr. Chambers : <br /> In response to the April 24 , 1996 decision filed by the <br /> California Court of Appeal, Third Appellate District, the <br /> Department of Toxic Substances Control (DTSC) has made a <br /> hazardous waste property determination regarding the subject <br /> property (Site) . DTSC concerns at the Site stem from the <br /> construction and use of a 16-acre reservoir by Southern Pacific <br /> Transportation Company to store "Bunker C" oil between 1926 and <br /> 1945 . In 1953 after a fire, the reservoir was collapsed and <br /> covered with native soil . Investigations into soil contamination <br /> revealed subsurface contamination with polynuclear aromatic <br /> hydrocarbons (PAHs) , a layer of asphalt-like material, and oil . <br /> In the past, DTSC required the performance of a Health Risk <br /> Assessment to determine the potential threat posed by PAH <br /> contamination in soil and in the asphalt-like material . DTSC <br /> also recommended additional groundwater monitoring to assess the <br /> migration of the oil . Further discussion is provided below. <br /> The PAH contamination associated with residues in the <br /> collapsed reservoir was identified at depths between five and <br /> eight feet . In 1991, DTSC calculated the lifetime cancer risk <br /> from carcinogenic PAHs to be 1 x 10'5 to 3 x 10-5. DTSC staff <br /> have re-calculated the potential risk from the carcinogenic PAHs <br /> using revised health risk criteria. DTSC has concluded that PAH <br /> levels detected in soil (assuming the same exposure assumptions <br /> used in past reports) do not represent a significant risk for <br /> unrestricted or residential land use. <br />